This invention relates to apparatus for electric discharge machining of the surface of a work roll and, more particularly, to a new electrode construction and electrode mounting arrangement for such apparatus.
The use of a satin or matte finished roll for cold rolling of steel sheet or strip in order to texture the surface of the finished product has been a practice in the steel industry for some time. One patent that discloses this practice and teaches a method for providing such a finish is Bills, et al, U.S. Pat. No. 3,754,873 issued Aug. 28, 1973 for a Cold Rolled Sheet. The Bills et al patent teaches that in order to effect a sanitized or textured surface on sheet or strip material, the rolls for processing the sheet or strip are textured. Texturing of the rolls is generally effected by electric discharge machining methods. Since the issuance of U.S. Pat. No. 3,754,873, there has been a series of patents relating to electrical discharge machining of steel cold forming rolls including the following patents:
______________________________________ Issue Reg. No. Inventor Title Date ______________________________________ 3,796,851 Pfaff, Jr. Apparatus for Making 3/12/74 Cylindrical Dies 3,800,117 Anderson EDM Apparatus for 3/26/74 Finishing Rolls Re. 28,027 Bills, et al Cold Rolling Work Roll 6/4/74 3,878,353 Anderson Method for Finishing Rolls 4/15/75 3,890,481 Buck Electroerosive Process for 6/17/75 Manufacturing Rotary Dies 3,941,970 Grow Feed Roll and Method of 3/2/76 Imparting A Rough Texture to the Surface Thereof 3,962,557 Buck Waste Metal Removal 6/8/76 in E. D. M. Machining Re. 29,399 Inoue Servosystem for Gap 9/13/77 Electrical Machining Processes (Especially Electroerosion) 4,219,718 Sato, et al Process and Apparatus for 8/26/80 Electrical Discharge Machining of Cylindrical Work 4,221,952 Sato, et al Electric Discharge 9/9/80 Machining Method 4,233,485 Sato, et al Process for Electrical 11/11/80 Discharge Machining of Cylindrical Work 4,242,557 Sato, et al Apparatus for 12/30/80 Electrical Discharge Machining of Cylindrical Work 4,287,403 Sato, et al Method and apparatus for 9/1/81 Adjusting the Gap in an Electric Discharge Machine ______________________________________
It will be noted that among the patents listed, are two U.S. Pat. No. 3,800,117 and U.S. Pat. No. 3,878,353, issued in the name of the present inventor. These patents disclose that rolls may be machined by electric discharge methods that call for mounting the roll partially submerged in a reservoir of dielectric fluid in opposed relation to a discharge electrode. The other prior art patents teach various electrode constructions, as well as various control circuitry for the electric discharge machining apparatus. Also, the various patents listed are not necessarily directed to methods for the manufacture of cold forming rolls, but, in fact, are directed to the general practice of electrical discharge machining apparatus and control equipment for such apparatus.
The present invention is particularly directed to electric discharge machining of rolls which would be used in the manufacture of sheet and strip and especially the apparatus for texturizing or for sanitizing such rolls. The invention has application, however, to texturizing a long shaft such as a temper mill work roll, a short shaft such as a crankshaft, a wear surface such as a cylinder opening, and a flat surface such as a machine slide surface.
Prior art apparatus and procedures, though successful and useful, are perceived to have some shortcomings. For example, control of the uniformity of the texture or pattern applied to the surface of the roll, particularly a roll which has a curved surface, has been difficult. Control of the machining operation itself by controlling the strength, duration and location of the electric discharge pulses has also been difficult. The present invention provides an apparatus which enhances the ability to control the electric discharge to a surface, particularly a surface having a simple curved or compound curved shape.